This section is surprisingly small because the rest of the FAQ is littered with answers involving regular expressions. For example, decoding a URL and checking whether something is a number are handled with regular expressions, but those answers are found elsewhere in this document (in perlfaq9: "How do I decode or create those %-encodings on the web" and perlfaq4: "How do I determine whether a scalar is a number/whole/integer/float", to be precise).
This section of the Perl FAQ covers questions involving operating system interaction. Topics include interprocess communication (IPC), control over the user-interface (keyboard, screen and pointing devices), and most anything else not related to data manipulation. Read the FAQs and documentation specific to the port of perl to your operating system (eg, perlvms, perlplan9, ...). These should contain more detailed information on the vagaries of your perl.